The present invention relates generally to valves used in oilfield and, more particularly, to seal assemblies for valves and methods of sealing valves.
Various types of valves are used in oilfield well exploration, drilling, and production equipment. Valves are coupled to a pipeline and are typically used to shut off or turn on the flow of a fluid, such as a liquid, gas or both. Valves are typically either unidirectional or bi-directional. In a unidirectional valve, the valve has to be placed only in one unique way in a pipeline so as to match the pressure direction. In a bi-directional valve, either side of the valve can be used as the upstream side, which allows the valve to be placed in a pipeline without any specific side facing the direction of pressure. Valve sealing components are usually symmetrical for ease of installation and maintenance and to achieve bi-directionality.
A gate valve is a type of valve that includes a substantially rectangular-shaped gate that is moved by an operator in and out of the valve body to control the fluid. The operator may be manual or may be actuated hydraulically, pneumatically or electrically, for example. A gate valve also includes an annular or ring-shaped seat member that seals against the gate. Depending on gate valve design, one seat member may be disposed on either side of the gate, or alternatively, additional seat members may be disposed adjacent the seat member, which members are involved in the sealing of the valve. The additional seat members seal the passage between the seat member and body pocket.
A valve body pocket generally houses the seal assembly. A valve seal assembly generally includes sealing members such as the seat member adjacent the valve engaging member and other associated seat members which may be referred to as a body bushing or pocket insert, as examples. A seal assembly also generally includes at least one seal ring, which provide a seal between the various seat members, valve body pocket and the gate. Expanding gate valves utilize expanding gate assembly structures comprising a gate element and segment, which are adapted to expand transversely of one another against the sealing rings.
Another type of valve design is a plug valve, where a cylindrical plug having a bore in the center thereof is used to either block fluid flow, or to allow fluid to pass through the valve by rotating the plug. When the plug bore is aligned in parallel with the valve bore, the valve is open and fluid flows through the plug. When the plug bore is aligned perpendicular to the valve bore, the valve is closed and fluid is blocked from flowing through the plug.
Gate valves are classified as either downstream or upstream sealing. For downstream sealing gate valve designs, the sealing is done at the downstream side of the valve. The downstream side of the valve is the side farthest from the pressure source. Therefore, a valve having a downstream sealing design seals on the side of the valve farthest from the pressure source. In contrast, a valve having an upstream sealing design seals on the side of the valve closest to the pressure source.
Various types of seal assemblies have been devised for such valves. With many of these, such as where the seats are press-fit into seat pockets in the valve body, the seats must be installed or removed for repair purposes using special tools and associated costly procedures.
Embodiments of the present invention achieve technical advantages as a valve seal assembly having an improved seal arrangement. Two seal members include a seat member adjacent a valve engaging member, and a pocket insert adjacent the seat member. The pocket insert fits fixedly within the valve body. A seal ring is disposed between the seat member and pocket insert, and two U-shaped seal rings are disposed between the pocket insert and the valve body.
Disclosed is a preferred embodiment for a valve sealing assembly for sealing a valve engaging member to a valve body. The sealing assembly includes a first annular seat member adapted to fixedly sealingly fit within the first annular valve body pocket, the first seat member having a substantially L-shaped cross-section, the L-shaped cross-section having a bottom and a side. A first annular groove is disposed within the first seat member L-shaped cross-section bottom, a second annular groove is disposed within the first seat member bottom, the second annular groove positioned concentrically with the first annular groove, and a first seal ring is disposed between the first seat member and the first valve body pocket within the first seat member first groove. A second seal ring is disposed between the first seat member and the first valve body pocket within the first seat member second groove, a second annular seat member is adapted to sealingly fit within the first seat member, the second seat member including an annular groove disposed over the first seat member L-shaped bottom, the second seat member being adapted to sealingly couple to the valve engaging member first face, and a third seal ring is disposed between the second seat member and the first seat member within the second seat member groove.
Also disclosed is a valve sealing assembly for sealing a valve engaging member to a valve body, the sealing assembly including a first annular seat member adapted to sealingly fit within one of the annular valve body pockets, the first seat member having a substantially L-shaped cross-section, the first seat member having an annular groove along the side exterior. At least one seal ring is disposed between the first seat member and the valve body pocket, and a second annular seat member is adapted to sealingly fit within the first seat member, the second seat member being adapted to sealingly couple to the valve engaging member. A first retainer ring is adapted to fit within the first seat member groove, wherein the first retainer ring is adapted to retain the first seat member within the valve body pocket, and at least one seal ring disposed between the first seat member and the second seat member.
Further disclosed is a valve sealing assembly for sealing a valve engaging member to a valve body, the sealing assembly including a first annular seat member adapted to sealingly fit within one of the annular valve body pockets, the first seat member having a substantially L-shaped cross-section, and at least one seal ring disposed between the first seat member and the valve body pocket. A second annular seat member is adapted to sealingly fit within the first seat member, the second seat member being adapted to sealingly couple to the valve engaging member and including an annular groove along the exterior. A first retainer ring is adapted to fit within the second seat member groove, wherein the second retainer ring is adapted to retain the second seat member within the first seat member, and at least one seal ring is disposed between the first seat member and the second seat member.
Also disclosed are methods of sealing a valve engaging member to a valve body about a borehole and a method of retaining a seat member within a valve.
Advantages of embodiments of the invention include providing an improved seal assembly for a valve engaging member. Embodiments of the seal assembly allow fluid to enter the valve cavity from the pipeline bore during pressure applications, and allow the pressure in the valve cavity to bleed with the pipeline bore. Pressure is not trapped in the valve body cavity when the valve engaging member is in the fully closed or open position. Well bore fluid is not passed between the seating element and the body pocket, which prevents erosion and corrosion of the body pocket. The pocket insert is fixed within the valve body pocket and is a sacrificial component, which provides a labor and cost savings by avoiding the repair of valve body pockets. Equilibrium is achieved inside the valve engaging member sealing assembly, preventing damage to the sealing mechanism and components. A support ring disposed within each U-shaped seal prevents the collapse of the U-shaped seals with exposure to pressure. The built-in lip prevents debris from entering the space between two seat members with a built-in lip. This prevents valve failure and prevents damage to seals and seat members. The retainer rings hold the pocket insert within a valve body pocket, or a seat member within a pocket insert, even when the valve bore is in the vertical position. This improves the ease of servicing and repairing the valve, for workmen no longer have to remove the valve and place it horizontally on the ground to repair it.